Phytate/calcium molar ratio does not predict accessibility of calcium in ready-to-eat dishes

Revisiting phytate-element interactions: implications for iron, zinc and calcium bioavailability, with emphasis on legumes

Myo-Inositol hexakisphosphate or phytic acid concentration is a prominent factor known to impede divalent element bioavailability in vegetal foods including legumes. Both in vivo and in vitro studies have suggested that phytic acid and other plant-based constituents may synergistically form insoluble complexes affecting bioavailability of essential elements. This review provides an overview of existing investigations on the role of phytic acid in the binding, solubility and bioavailability of iron, zinc and calcium with a focus on legumes. Given the presence of various interference factors within legume matrices, current findings suggest that the commonly adapted approach of using phytic acid-element molar ratios as a bioavailability predictor may only be valid in limited circumstances. In particular, differences between protein properties and molar concentrations of other interacting ions are likely responsible for the observed poor correlations. The role of phytate degradation in element bioavailability has been previously examined, and in this review we re-emphasize its importance as a tool to enhance mineral bioavailability of mineral fortified legume crops. Food processing strategies to achieve phytate reduction were identified as promising tools to increase mineral bioavailability and included germination and fermentation, particularly when other bioavailability promoters (e.g. NaCl) are simultaneously added.

Effects of extruded whole-grain sorghum (Sorghum bicolor (L.) Moench) based diets on calcium absorption and bone health of growing Wistar rats

Apparent calcium absorption, total bone mineral content and density, and mineral contents of the right femur were studied using a growing rat model. Twenty-four male Wistar rats were fed with diets based on extruded whole grain red (RSD) or white sorghum (WSD), and control diet (CD) up to 60 days. The animals fed with sorghum diets consumed less and gained less weight compared to those fed with CD, but the efficiency of all diets was similar. Calcium intake was lower in animals fed with sorghum diets, related to the lower total intake of these animals. Apparent calcium absorption in animals fed with RSD was lower than in those fed with CD (CD: 72.7%, RSD: 51.0%, WSD: 64.8%). No significant differences in bone mineral density of total body, spin, femur, distal femur, tibia and proximal tibia were observed among the groups. However, Ca and P contents in the right femur of the rats consuming RSD were lower, indicating a certain imbalance in the metabolism of these minerals.

Effect of sprouting on nutritional quality of pulses

In order to investigate the nutritional quality of industrial-scale sprouted versus unsprouted chickpeas and green peas, before and after cooking, the ultrastructure, chemical composition, antioxidant capacity, starch digestibility, mineral content and accessibility were analysed. Sprouting did not deeply affect raw seed structure, although after cooking starch granules appeared more porous and swelled. Chemical composition of raw sprouted seeds was not strongly affected, excepting an increase in protein (both pulses), and in free sugars (in peas; +10% and +80%, respectively, p < .05). The industrial sprouting favoured phytic acid leaching in cooking water (-35% in seeds, compared to unsprouted cooked ones, p < .05), and promoted antioxidant capacity reductions in raw and cooked seeds (-10% and -37%, respectively, p < .05). In conclusion, sprouting on an industrial-scale induced mild structural modifications in chickpeas and peas, sufficient to reduce antinutritional factors, without strongly influencing their nutritional quality. These products could represent nutritionally interesting ingredients for different dietary patterns as well as for enriched cereal-based foods.

The influence of dietary fat and intestinal pH on calcium bioaccessibility: anin vitrostudy

In vivostudies measuring true fractional calcium (Ca) absorption have shown that dietary fat is a significant predictor of absorption and is influenced by luminal pH levels.